Conventionally, there are used many disk cartridges each of which houses a disk such as an optical disk or the like rotatably therein and is inserted into a disk drive unit which writes and/or reads information signals to and/or from the disk loaded into place while being still held in the disk cartridge. The disk cartridge of this type houses in a cartridge body thereof a disk to be protected, and permits easy insertion and ejection of the disk into and out of the disk drive unit.
To load a disk housed in the cartridge body of the disk cartridge into the disk drive unit, the cartridge body has formed therein a write and/or read opening (will be referred to as “write/read opening” or “head opening” hereunder) through which a part of the disk can be exposed to outside in a range between the inner and outer radii thereof. A write/read head provided at the disk drive unit, such as an optical pickup, is opposite to the disk through the write/read opening and scans the signal recording area on the disk to write or read information signals to or from the disk.
Note here that if the write/read opening formed in the cartridge body is left uncovered, dust or the like will possibly enter the cartridge body and contaminate the disk housed in the cartridge body when the disk cartridge is not used in any disk drive unit, such as during storage or the like.
On this account, the disk cartridge housing a disk is provided with a shutter member to cover the write/read opening (head opening). There has been proposed a disk cartridge provided with such a shutter member as well as with a spring member which forces the shutter member to cover the write/read opening in order to prevent the write/read opening from being uncovered while the disk cartridge is not in use.
A disk cartridge having provided therein a forcing member such as a spring member to force the shutter member in a direction to cover the write/read opening is known from the disclosure in the Japanese Patent Application Laid Open No. 91915 of 1997.
In the conventional disk cartridges provided with a shutter member, including the one disclosed in the above Japanese Patent Application Laid Open No. 91915 of 1997, the shutter member is forced by a forcing member only in the direction to cover the write/read opening.
To positively uncover the write/read opening covered with the shutter member having been forced only in the covering direction, the shutter member has to be further moved from the position to uncover the write/read opening, namely, an over-stroke of the shutter member is required. As the result, the shutter member has to be moved in a larger range, which will make it difficult to design the disk cartridge more compact. When a disk cartridge designed for such an over-stroke of the shutter member is loaded in the disk drive unit and shutter member is held in the position to uncover the write/read opening against the force of the forcing member, a backlash will arise. Such a shutter member will be swayed even with a small vibration and cannot be held stably in the position to uncover the write/read opening. Such a sway of the shutter member will have an influence on the write/read performance of the disk drive unit and hence no quality write/read performance cannot be assured.
Also, in a disk drive unit compatible with a disk cartridge provided with a forcing member to force the shutter member only in a direction to cover the write/read opening, a holding mechanism to hold the shutter member in a position to uncover the write/read opening against the force of the forcing member will lead to a complicated construction of the disk drive unit. Further, the holding mechanism should have a sufficient power to hold the shutter member in the position to uncover the write/read opening against the force of the forcing member for the shutter member. Therefore, the mechanism itself is unavoidably larger, resulting in a difficulty to design the disk drive unit itself more compact and lightweight.
In addition to the aforementioned disk cartridge, there has also been proposed a disk cartridge having installed pivotably inside a cartridge body thereof a return helical spring fixed at one end thereof to a shutter member to force the latter in any selected one of directions to uncover and cover the write/read opening. In the disk cartridge of this type, when the return helical spring reverses its course as the shutter member is moved to uncover or cover the write/read opening, it will start forcing in the opposite direction. Thus, when the shutter member is moved in a direction to uncover the write/read opening, the return helical spring will force the shutter member toward a position to uncover the write/read opening and hold it in that position. On the other hand, when the shutter member is moved in a direction to cover the write/read opening, the return helical spring will force the shutter member toward a position to cover the write/read opening and hold it in that position.
Since it is difficult to provide such a return helical spring in the cartridge body after upper and lower halves of the cartridge body are butt-joined to each other, the return helical spring has to be provided pivotably inside the cartridge body in advance and then connected to the shutter member.
However, it is difficult to simultaneously assemble the shutter member to the cartridge body and fix the return helical spring to the shutter member and it is necessary to prevent the return helical spring from being disengaged from the shutter member when the latter is moved to uncover or cover the write/read opening.
Also, the free end of the return helical spring provided inside the cartridge body will possibly be freely pivotable inside the cartridge body, touch and scratch the disk until the shutter member is installed to the cartridge body.